1. Technical Field
The present application relates generally to medical devices, and more particularly, to a hemostatic valve assembly for controlling the flow of fluids through a medical device.
2. Background Information
A variety of well-known medical procedures are performed by introducing an interventional device such as a catheter, trocar, sheath, stent and the like into a vessel in a patient's body. Typical procedures for introducing an interventional device into a blood vessel include the well-known Seldinger technique. The Seldinger technique involves opening a blood vessel with a needle, inserting a wire guide into the vessel through the lumen of the needle, withdrawing the needle and inserting a dilator over the wire guide. The dilator is located inside an introducer sheath which is also inserted into the vessel, and the dilator is sealed to the sheath by a hemostatic valve through which the dilator passes. The dilator is thereafter removed, and an interventional device is inserted through the sheath and hemostatic valve into the vessel.
During performance of the Seldinger technique and other interventional procedures, care must be taken to avoid the undesirable introduction or leakage of air into the vessel (air embolism), as well as the undesirable leakage of blood, other bodily fluids or cavity-pressurizing gas from the patient. As procedures for introducing catheters and other interventional devices have become more widely accepted, the procedures have become more diverse, and the variety of sizes and types of such devices employed has grown dramatically. As a result, the risk of inward or outward leakage of fluids has increased.
One known way to minimize such leakage is to provide one or more disk-like gaskets in an elongated passageway of a device through which fluids may pass into or out of the body. Such disks have opposing surfaces and often include one or more slits extending partially across each of said surfaces and extending inwardly toward the interior of the disk. A generally axial opening is provided between the slits to provide a sealable path for insertion of an interventional device through the disks. Such disks are described in, among others, U.S. Pat. Nos. 5,006,113 and 6,416,499, assigned to the assignee herein. The '113 and the '499 patents are incorporated by reference. Such devices are generally effective for sealing large diameter devices, but are often less effective for sealing smaller diameter devices, particularly after the earlier passage of a large diameter device.
Another type of valve that is presently in use for sealing elongated passages in a medical device to prevent passage of fluids is known as an iris valve. An iris valve is described in U.S. Pat. No. 5,158,553, incorporated by reference herein. The valve described in the '553 patent comprises a valve hub that is joined to a catheter-type device, and a rotatable cap that is joined to the hub. An elastomeric sleeve is positioned in an opening through the interior of the valve body. Each end of the elastomeric sleeve is joined to the rotatable cap by wrapping and clamping the respective end around a clamping mechanism. When the cap is rotated in a first direction, the circular opening of the elastomeric sleeve is fully opened. When the cap is rotated in a second direction opposite the first direction, the elastomeric sleeve is twisted intermediate the two ends to effect closure of the circular opening. Due to the elastomeric properties of the sleeve, the circular opening of the elastomeric sleeve constricts as the cap is rotated to effect closure.
Although the valve of the '553 patent is generally effective for sealing sheaths of certain sizes and compositions, the general design of the valve assembly of the '553 patent has certain shortcomings. For example, the manner of engaging the ends of the seal to the respective hub and cap is less than optimal. Such ends are capable of disengagement, which destroys the ability of the valve to form a seal. In addition, the seal does not include provisions to prevent recoil of the seal after rotation of the rotatable cap to position the seal in a desired position. As a result, if the operator relaxes the rotational pressure on the valve, the seal can revert, or recoil, to its original (unsealed) position. Yet another problem with the iris valve assembly as described in the '553 patent is that longitudinally extending gaps or channels are capable of being formed along the seal, which gaps or channels can extend through the valve after rotation of the valve to the closed position. When such gaps or channels are present, fluid can leak through them in the valve seal. Furthermore, the configuration of such valves renders them subject to tearing.
It would be desirable to provide a valve assembly that overcomes the problems associated with prior art iris valves, and that effectively combines the advantages of disk valves and iris valves. It would be desirable to provide an iris valve that provides an effective seal of the internal passageway of an introducer sheath or like medical device with a high degree of effectiveness when no interventional device lies across the seal or valve, and that is also capable of providing an acceptable seal when devices of varying diameters are introduced therein. It would also be desirable to provide an iris valve capable of inhibiting recoil following rotation of the valve member, and that has axial ends that are securely affixed in the valve. It would further be desirable to provide an iris valve that is capable of resisting the formation of gaps or channels, and is capable of resisting tearing when penetrated by an interventional device of large diameter. Finally, it would also be desirable to have a seal that tolerates repeated insertions and withdrawals of interventional devices without appreciable decrease in the performance characteristics of the seal or valve.